Die cushion apparatus of press machine

ABSTRACT

A die cushion apparatus of a press machine which makes possible to manufacture a plurality of types of products of different sizes by one press machine and capable of minimizing a production facility, and which comprises a plurality of die cushion units, each having a cushion pad and a rise and fall drive unit for vertically driving the cushion pad, that are aligned in a direction perpendicular to a work conveying direction, and a control unit capable of individually and independently controlling the plurality of die cushion units.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser. No. 11/180,732, filed Jul. 14, 2006, which is based on Japanese Patent Application No. 2004-209699, filed on Jul. 16, 2004, and Japanese Patent Application No. 2005-118514, filed on Apr. 15, 2005, the disclosures of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a die cushion apparatus of a press machine, and more particularly to a die cushion apparatus suitable for a press machine of a production facility for manufacturing various types of products of different sizes.

2. Description of the Related Art

A press machine A for executing drawing work, as shown in FIG. 16, includes a lower die (punch) E mounted on a bed B and an upper die (die) U mounted to a slide S, and includes a blank holder H operated to rise or fall through a cushion rod R by a die cushion apparatus C installed in the bed B.

The die cushion apparatus C includes a cushion pad Cp provided to be vertically movable in the bed B, and an oil pressure servo cylinder Cs for rising and lowering the cushion pad Cp. The die cushion apparatus C, when drawing a work W by lowering the slide S, operates to prevent a “crack,” a “wrinkle,” etc. from occurring in the product by pressing the work W to the upper die U at a predetermined pressure through the blank holder H.

Also, the die cushion apparatus C is controlled to sequentially operate a preliminary acceleration stroke a, a drawing stroke b, an auxiliary lift c, locking d, etc., as shown by a solid line (die cushion motion) with a motion (broken line) of the slide S (upper die U) as shown in FIG. 17 based on position information of the blank holder H and pressure information to the work W.

Incidentally, the die cushion apparatus of the press machine is not only used as a means for driving the blank holder, but also it is used, without saying, as a buffer device and a lifting device of the product with various type pressing, such as “drawing,” “bending,” “cutting,” etc.

Meantime, a body of an automobile is noted as a typical product manufactured by frequently using a pressing work, however, since types of panels that form one automobile are various, there has been a problem that the production facility becomes uselessly large in scale.

More particularly, the panels forming one automobile are largely classified, as shown in FIGS. 18A to 18C, into three types of a class A panel (a large size product) Pa, such as a roof panel, a floor pan, etc., a class B panel (an intermediate size product) Pb, such as a door panel, a hood panel, etc, and a class C panel (a small size product) Pc, such as various types of pillars, a cross member, etc. The class A panel Pa is manufactured in a press working line (tandem press line) PLa in which a plurality of specialized press machines Aa are aligned in parallel through a work loader T, the class B panel Pb is manufactured in a press working line (tandem press line) PLb in which a plurality of specialized press machines Ab are aligned in parallel through the work loader T, and further the class C panel Pc is manufactured in a press working line (tandem press line) PLc in which a plurality of specialized press machines Ac are aligned in parallel through the work loader T.

Thus, in the conventional production facility, since the class A panel Pa, the class B panel Pb and the class C panel Pc are respectively manufactured by the specialized press machine Aa, press machine Ab and press machine Ac, a plurality of press working lines are required to manufacture all the panels forming one automobile, and an inconvenience of introducing a large scale of the production facility has not been avoided.

In view of the above-mentioned fact, an object of the present invention is to provide a die cushion apparatus of a press machine which can manufacture a plurality of types of products having different sizes by one press machine and which can also achieve minimization of the production facility.

SUMMARY OF THE INVENTION

A first aspect of the present invention provides a die cushion apparatus of a press machine, comprising a plurality of die cushion units each having a cushion pad and an elevating drive unit for vertically moving the cushion pad, aligned in a bed in a direction perpendicular to a work conveying direction.

According to the die cushion apparatus of the first aspect of the invention, the plurality of die cushion units are provided in parallel along a direction perpendicular to the work conveying direction, a plurality of types of products can be manufactured by one press machine.

Further, according to the die cushion apparatus of the first aspect of the invention, since the plurality of types of products having different sizes are manufactured by one press machine, a production facility for manufacturing a large variety of types of products can be minimized as much as possible.

A second aspect of the present invention provides the die cushion apparatus according to the first aspect of the invention, which further comprises a control unit capable of individually and independently controlling the plurality of die cushion units.

According to the die cushion apparatus of the press machine of the second aspect of the invention, since the die cushion apparatus comprises the control unit for individually and independently controlling the plurality of die cushion units, it is possible to operate individual die cushion units for separate works or to operate only a specific die cushion unit.

A third aspect of the present invention provides the die cushion apparatus of a press machine according to the second aspect of the invention, wherein the control unit controls a plurality of die cushion units in synchronism with each other that are operated for a work common to each other.

According to the die cushion apparatus of a press machine of the third aspect of the invention, since a plurality of die cushion units, which operate on a common work, can be controlled in synchronism with each other, it is possible to make a work of a size extending over the plurality of die cushion units.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional front view schematically showing an embodiment of a die cushion apparatus of a press machine according to the present invention;

FIG. 2 is a plan view of an essential portion showing an embodiment of the die cushion apparatus according to the present invention;

FIG. 3 is a sectional view taken along a line III-III in FIG. 2 showing one embodiment of the die cushion apparatus according to the present invention;

FIG. 4 is a structural view of a control system in the die cushion apparatus shown in FIG. 1;

FIG. 5A, FIG. 5B and FIG. 5C are schematic plan views respectively showing operation modes of the die cushion apparatus according to types of products;

FIG. 6 is a conceptual view showing a structure of the die cushion apparatus when a small size product is manufactured;

FIG. 7 is an appearance perspective view showing a structure of a general mold;

FIG. 8 is a conceptual view showing a structure of the die cushion apparatus when an intermediate size product is manufactured;

FIG. 9 is a conceptual view showing a structure of the die cushion apparatus when a large size product is manufactured;

FIG. 10A and FIG. 10B are conceptual plan views showing operation modes of the die cushion apparatus according to types of products;

FIG. 11A and FIG. 11B are conceptual plan views showing operation modes of the die cushion apparatus according to types of products;

FIG. 12 is a schematic view showing another embodiment of a die cushion unit in the die cushion apparatus of the present invention;

FIG. 13 is a schematic view showing another embodiment of a die cushion unit in the die cushion apparatus of the present invention;

FIG. 14 is a schematic view showing another embodiment of a die cushion unit in the die cushion apparatus of the present invention;

FIG. 15 is a schematic view showing another embodiment of a die cushion unit in the die cushion apparatus of the present invention;

FIG. 16 is an entire conceptual view showing a conventional press machine;

FIG. 17 is an operation diagram showing the state of a motion in the die cushion apparatus; and

FIG. 18A, FIG. 18B and FIG. 18C are conceptual plan views showing a press working line built by using a conventional press machine.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will be described in detail based on the accompanied drawings.

FIG. 1 to FIG. 4 show an example of the die cushion apparatus of the present invention which is applied to a press machine for processing a work (metal plate) into a panel of a desired shape in a production facility of, for example, an automobile. Incidentally, since the entire structure of the press machine is not fundamentally different from the conventional press machine A shown in FIG. 16, a detailed description concerning the entire structure of the press machine will be omitted.

As shown in FIG. 1 to FIG. 3, a first unit (die cushion unit) 11, a second unit (die cushion unit) 12, a third unit (die cushion unit) 13 and a fourth unit (die cushion unit) 14 that constitute a die cushion apparatus 10 are provided in a base (bed) 2 of a press machine 1 installed on a floor.

The first unit 11 includes a cushion pad 11P having a rectangular shape viewed from above (plane view), and a pair of oil pressure servo cylinders 11S, 11S which are raising and lowering drive means for vertically moving the cushion pad 11P.

The cushion pad 11P is contained in one of four sections obtained by partitioning a peripheral wall 2A of the base 2 by partition walls 2B, and installed to be vertically movable with respect to the base 2 by slidably contacting a base guide g with a pad liner 1.

Furthermore, the pair of oil pressure servo cylinders 11S, 11S are fixed to a beam 2C installed in the base 2, and synchronously operated like one oil pressure servo cylinder, by connecting mutual oil paths by pipes 11 p.

Needless to say, the oil pressure servo cylinder 11S has a structure which can suitably change a pressure of a blank holder (a wrinkle suppressing pressure), a stroke, a locking position, etc., similarly to the oil pressure servo cylinder in a conventional die cushion apparatus.

The second unit 12 also includes a cushion pad 12P having a rectangular shape viewed from above (plane view), and a pair of oil pressure servo cylinders 12S, 12S, similarly to the first unit 11. The cushion pad 12P is installed and contained vertically movably in one section of the base 2, and the pair of oil pressure servo cylinders 12S, 12S are constructed to operate like one oil pressure servo cylinder.

Also, the third unit 13 includes a cushion pad 13P having a rectangular shape viewed from above (plane view), and a pair of oil pressure servo cylinders 13S, 13S, similarly to the first unit 11, and the cushion pad 13P is installed and contained vertically movably in one section of the base 2, and the pair of oil pressure servo cylinders 13S, 13S are operated like one oil pressure servo cylinder.

Furthermore, the fourth unit 14 also includes a cushion pad 14P having a rectangular shape viewed from above (plane view), and a pair of oil pressure servo cylinders 14S, 14S, similarly to the first unit 11. The cushion pad 14P is installed and contained vertically movably in one section of the base 2, and the pair of oil pressure servo cylinders 14S, 14S are operated like one oil pressure servo cylinder.

Here, the first unit 11, the second unit 12, the third unit 13 and the fourth unit 14 are provided to be aligned in a direction perpendicular to a work conveying direction (a direction perpendicular to the surface of paper in FIG. 1). Thus, the cushion pads 11P, 12P, 13P and 14P in the units 11 to 14 are arranged as if one large die cushion pad was divided into four in the direction perpendicular to the work conveying direction.

More particularly, the first unit 11, the second unit 12, the third unit 13 and the fourth unit 14 are laid out in a positional state for use simultaneously in one step of pressing, and further, laid out so that a work and a product are conveyed simultaneously by a work conveying unit such as a vacuum cup, etc. extended in the direction perpendicular to the work conveying direction.

On the other hand, the die cushion apparatus 10 has an operation controller 20 for controlling to operate the first unit 11, the second unit 12, the third unit 13 and the fourth unit 14 independently from each other or synchronously with each other, to be described later.

The operation controller 20 has a first controller 21 for independently controlling the first unit 11, and this first controller 21 controls to operate the first unit 11 in a predetermined die cushion motion (refer to FIG. 17) based on position information and pressure information, similarly to the conventional die cushion apparatus.

Furthermore, the operation controller 20 has a second controller 22 for independently controlling the second unit 12, a third controller 23 for independently controlling the third unit 13, and a fourth controller 24 for independently controlling the forth unit 14. These second controller 22 to the fourth controller 24 control to operate the second unit 12 to the fourth unit 14 in a predetermined die cushion motion (refer to FIG. 17) based on position information and pressure information, similarly to the first controller 21.

The operation controller 20 has a supervising controller 25 together with the first controller 21 to the fourth controller 24. This supervising controller 25 outputs a command signal to the first controller 21 to the fourth controller 24 to be described later based on a working state inputted from an operation panel 26, etc. of the press machine 1 to thereby supervise the independent operation control of the first unit 11, the second unit 12, the third unit 13 and the fourth unit 14 and also control to operate synchronously with each other in an arbitrary combination of the first unit 11 to the fourth unit 14.

Incidentally, in the press machine 1, a class A panel, such as a roof panel, etc., of a large size product, a class B panel, such as a door panel, etc. of an intermediate size product, and a class C panel, such as a cross member, etc. of a small size product can be used as an object to be worked. As shown in FIG. 5A, when an object to be worked is the class A panel Pa, all the first unit 11 to the fourth unit 14 are used for manufacturing a common one class A panel Pa.

Also, as shown in FIG. 5B, when an object to be worked is the class B panel Pb, the first unit 11 and the second unit 12, which are adjacent to each other, and the third unit 13 and the fourth unit 14, which are adjacent to each other, are used for manufacturing a common one class B panel Pb, respectively, and totally two class B panels Pb, Pb are manufactured.

Furthermore, as shown in FIG. 5C, an object to be worked is the class C panel Pc, all the first unit 11 to the fourth unit 14 are used for manufacturing the class C panels Pc, respectively, and totally four class C panels Pc, Pc, Pc, Pc are manufactured.

Here, FIG. 1 and FIG. 4 show an embodiment when the class C panel (small size product) Pc like FIG. 5C is an object to be worked, and in the base 2 of the press machine 1, a lower die L1, a lower die L2, a lower die L3 and a lower die L4 are installed respectively in an upper area of the first unit 1, the second unit 12, the third unit 13 and the fourth unit 14.

A blank holder H1, a blank holder H2, a blank holder H3 and a blank holder H4 are installed in the upper area of the first unit 1, the second unit 12, the third unit 13 and the fourth unit 14 through a cushion pin CP1, a cushion pin CP2, a cushion pin CP3 and a cushion pin CP4.

On the other hand, in the slide of the press machine 1, an upper die U1, an upper die U2, an upper die U3 and an upper die U4 are mounted at positions opposed to the lower die L1, the lower die L2, the lower die L3 and the lower die L4 through holders 5, respectively.

In the following description, in the press machine 1 of the above-mentioned structure, one scope of controlling to operate to the first unit 11 to the fourth unit 14 when the class A panel Pa, the class B panel Pb, and the class C panel Pc shown in FIG. 5A, FIG. 5B and FIG. 5C are manufactured will be described with reference to FIG. 1 and FIG. 4 showing the entire structure of the die cushion apparatus 10.

In the press machine 1 of the above-mentioned structure, when the four class C panel Pc (refer to FIG. 5C) of the same shape are manufactured at the same time, as shown in FIG. 6, the lower dies L1 to L4, and blank holders H1 to H4 are installed in the upper area of the first unit 11 to the fourth unit 14 in the bed 2, the upper dies U1 to U4 corresponding to the lower dies L1 to L4 are installed in the slide 4, and works Wc of the class C panel Pc is supplied to the individual dies.

An operation controller 20 of the die cushion apparatus 10 controls to operate the first unit 11 to the fourth unit 14 in a predetermined die cushion motion (refer to FIG. 17) corresponding to the specification of the class C panel Pc independently from each other by the first controller 21 to the fourth controller 24 based on the working state (“four class C panels are manufactured,” “specification of class C panel,” etc.) inputted from a control panel 26.

Incidentally, as shown in FIG. 7, square-rod shape heel guides La and heel guides Ua are projected from four corners of the lower die L1 and the upper die U1. The blank holder H1 is vertically moved with respect to the lower die L1 while the blank holder H1 is guided by the heel guide Ua by slidably contacting guide recesses Ha at four comers of the blank holder H1 with the heel guide Ua.

The oil pressure servo cylinders 11S, 11S of the first unit 11 for vertically moving the blank holder H1 are installed in parallel along the work conveying direction as shown in FIG. 3, but are connected via pipings 11 p, 11 p as described above, to operate like one oil pressure servo cylinder. Incidentally, a structure may be provided so that one oil pressure servo cylinder is provided.

On the other hand, in the press machine 1 of the above-mentioned structure, when the two class B panels Pb (refer to FIG. 5B) are manufactured simultaneously, as shown in FIG. 8, the lower die L11 and the lower die L12, and the blank holder H11 and the blank holder H12 are installed in the upper area of the first unit 11 and the second unit 12 and in the upper area of the third unit 13 and the fourth unit 14, and the upper die U11 and the upper die 12 corresponding to the lower die L11 and the lower die 12 are installed in the slide 4, and works Wb of the class B panel Pb are supplied to the individual dies.

The operation controller 20 of the die cushion apparatus 10 controls to operate the first unit 11, the second unit 12, the third unit 13 and the fourth unit 14 in a predetermined die cushion motion (refer to FIG. 17) corresponding to the specification of the class B panel Pb based on the working states (“two class B panels are manufactured,” “a common work for the first unit 11 and the second unit 12 is an object to be worked,” “a common work for the third unit 13 and the fourth unit 14 is an object to be worked,” and “specification of class B panel,” etc.) inputted from the control panel 26.

Here, in the operation controller 20, the first unit 11 and the second unit 12 provided to manufacture the one class B panel Pb are controlled to be operated synchronously with each other, and the third unit 13 and the fourth unit 14 provided to manufacture the other class B panel Pb are controlled to be operated synchronously with each other.

More particularly, the first unit 11 and the second unit 12 are controlled to be operated synchronously with each other in such a manner that the first unit 11 is controlled to be operated based on a command signal from the first controller 21 and the second unit 12 is controlled to be operated based on a feedback signal with the operation of the first unit 11, by a so-called master/slave type controlling method.

Similarly, the third unit 13 and the fourth unit 14 are controlled to be operated synchronously with each other in such a manner that the third unit 13 is controlled to be operated based on a command signal from the third controller 23 and the fourth unit 14 is controlled to be operated based on a feedback signal with the operation of the third unit 13, by a so-called master/slave type controlling method.

In this manner, the first unit 11 and the second unit 12, and the third unit 13 and the fourth unit 14 are controlled to be operated synchronously with each other, and the blank holder H11 and the blank holder H12 vertically move without inclining in a direction perpendicular to the work conveying direction, and hence a damage of a die unit due to an inclination of the blank holder is prevented.

Incidentally, whether any of the first unit 11 and the second unit 12 with the common work Wb as an object to be worked is used as a master of the operation control or whether any of the third unit 13 and the fourth unit 14 with the common work Wb as an object to be worked is used as a master of the operation control can be, of course, suitably set in view of various conditions.

On the other hand, in the press machine 1 of the above-mentioned structure, when one class A panel Pa (refer to FIG. 5A) is manufactured, as shown in FIG. 9, one lower die L20 and one blank holder H20 are installed in the upper area of the first unit 11 to the fourth unit 14 in the bed 2, and the upper die U20 corresponding to the lower die L20 is installed in the slide 4, and the work Wa of the class A panel Pa is supplied.

The operation controller 20 of the die cushion apparatus 10 controls to operate the first unit 11, the second unit 12, the third unit 13 and the fourth unit 14 in a predetermined die cushion motion (refer to FIG. 17) corresponding to the specification of the class A panel Pa based on the working states (“one class A panel is manufactured,” “a common work in the first unit 11 to the fourth unit 14 is an object to be worked,” “specification of the class A panel,” etc.) inputted from the control panel 26.

Here, in the operation controller 20, the first unit 11, the second unit 12, the third unit 13 and the fourth unit 14 are controlled to be operated synchronously with each other.

More particularly, the first unit 11 is controlled to be operated based on the command signal from the first controller 21, and the second unit 12, the third unit 13 and the fourth unit 14 are controlled to be operated based on the feedback signal with the operation of this first unit 11, synchronously with each other by a so-called master-slave type controlling method.

Thus, the first unit 11, the second unit 12, the third unit 13 and the fourth unit 14 are controlled to be operated synchronously with each other, and the blank holder H20 is thereby vertically moved without any inclination in a direction perpendicular to the work conveying direction, and hence a damage of the die unit due to the inclination of the blank holder is prevented.

Incidentally, any of the first unit 11 to the fourth unit 14 with a common work Wa as an object to be worked can be suitably set as a master for operation control in view of various conditions.

Thus, according to the press machine 1 adopting the die cushion apparatus 10 concerning the present invention, by using a different work as an object to be worked for each of the individual die cushion units of the first unit 11 to the fourth unit 14, or by using a common work as an object to be worked for the combination of die cushion units, products of a plurality of types having different sizes can be manufactured by one press machine 1.

Further, according to the die cushion apparatus 10 of the above-mentioned structure, since products of a plurality of types having different sizes can be manufactured by one press machine 1, a production facility for manufacturing a wide variety of types of products can be minimized as much as possible.

Incidentally, as shown in FIG. 10A, when four class C panels Pc1, Pc2, Pc3, and Pc4 having largely different shapes (specification) are manufactured, the lower dies L1 to L4, the blank holders H1 to H4, and the upper dies U1 to U4, which are respectively for the class C panels Pc1 to Pc4, are used, and works Wc, Wc, Wc, and Wc of the class C panels Pc1 to Pc4 are supplied to the individual dies.

The operation controller 20 of the die cushion apparatus 10 is controlled to be operated in a predetermined die cushion motion (refer to FIG. 17) corresponding to the specification of the class C panel Pc independent from each other by the first controller 21 to the fourth controller 24 based on the working state inputted from the control panel 26.

More particularly, the first unit 11 to the fourth unit 14 are controlled to be operated independently along with pressure of a blank holder, stroke, operating timing, etc. corresponding to the specifications of the class C panels Pc1 to Pc4.

Particularly, rising speeds of the first unit 11 to the fourth unit 14 are controlled so that the timings of the respective blank holders H1 to H4 reaching a predetermined lift rising end responding to a shape of a product become the same irrespective of a difference of the stroke due to a depth of drawing, etc. by considering a removal of the product by a work conveying unit, such as a vacuum cup, etc.

Thus, in the press machine 1 adopting the die cushion apparatus 10 according to the present invention, a plurality of the products having the same types (class B panel, class C panel) and largely different shapes (specifications) can be manufactured simultaneously in the same step.

On the other hand, as shown in FIG. 10B, when two class C panels Pc, Pc and one class B panel Pb are manufactured, as shown in FIG. 6, the lower dies L1, L2, the blank holders H1, H2, and the upper dies U1, U2 are installed, as shown in FIG. 8, the lower dies L12, the blank holder H12, and the upper die U12 are installed, works Wc, Wc of the class C panel Pc are supplied between the lower dies L1, L112 and the upper dies U1, U2, and the work Wb of the class B panel Pb is supplied between the lower die L12 and the upper die U12.

The operation controller 20 of the die cushion apparatus 10 controls to operate the first unit 11 and the second unit 12 by the first controller 21 and the second controller 22 in a predetermined die cushion (refer to FIG. 17) corresponding to the specification of the class C panel Pc independently from each other based on the working state inputted from the control panel 26, and controls to operate the third unit 13 and the fourth unit 14 used to manufacture the class B panel Pb in a predetermined die cushion motion (refer to FIG. 17) corresponding to the specification of the class B panel Pb synchronously with each other.

Also, the operation controller 20 controls the rising speeds of the first unit 11 to the fourth unit 14 so that the respective blank holders H1 to H4 become the same timings to reach a predetermined lift rising end responding to the shape of the product irrespective of the difference of the stroke due to the depth of the drawing, etc. by considering the removal of the product by the work conveying unit, such as a vacuum cup, etc.

Thus, in the press machine 1 adopting the die cushion apparatus 10 according to the present invention, a plurality of types of the products (class B panel, class C panel) having different sizes can be manufactured simultaneously in the same step.

Also, as shown in FIG. 11A, when one class B panel Pb is manufactured, as shown in FIG. 8, the lower die L11, the blank holder H11, and the upper side U11 are installed, and the work Wb of the class B panel is supplied between the lower die L11 and the upper die U11.

The operation controller 20 of the die cushion apparatus 10 controls to operate the second unit and the third unit used to manufacture the class B panel Pb based on the working state inputted from the control panel in a predetermined die cushion motion (refer to FIG. 17) corresponding to the specification of the class B panel Pb synchronously with each other.

Further, as shown in FIG. 11B, when the two class C panels Pc, Pc are manufactured, as shown in FIG. 6, the lower dies L2, L3, the blank holders H2, H3, and the upper dies U2, U3 are installed, and the work Wc of the class C panel Pc is supplied between the lower dies L2, L3 and the upper dies U2, U3.

The operation controller 20 of the die cushion apparatus 10 controls to operate the second unit and the third unit used to manufacture the class C panel Pc by the second controller 22 and the third controller 23 based on the working state inputted from the control panel in a predetermined die cushion motion (refer to FIG. 17) corresponding to the specification of the class C panel Pc independently from each other.

Thus, in the press machine 1 adopting the die cushion apparatus 10 according to the present invention, the specific die cushion may not be used. Further, which die cushion is selected can be set freely. It is needless to say that a die cushion should be selected so that an eccentric load generated at the working time may become as small as possible.

Here, in the above-mentioned embodiment, a plurality of die cushion units in which common works to each other are used as objects to be worked are controlled to be operated synchronously with each other by a master/slave type controlling method. However, as a structure for embodying the master/slave type controlling method, various existing structures may be suitably adopted.

Also, as a method for controlling to operate a plurality of die cushion units synchronously with each other, not only the master/slave type controlling method exemplified in the embodiment, but also existing various type controlling method may be, of course, effectively applied.

Further, in the above-mentioned embodiment, a rise and fall drive unit of the die cushion unit in the die cushion apparatus is exemplified in the example constructed by the oil pressure servo cylinder. However, for example, the rise and fall drive unit of the die cushion unit can be constructed by a suitable drive means, such as, for example, a motor-driven servo motor, etc.

FIG. 12 is a schematic view showing another embodiment of the die cushion unit. In this die cushion unit 100, a cushion pad 101 is interconnected to a motor-driven servo motor 107 through a ball screw 102, a coupling member 103, a large pulley 104, a belt 105 and a small pulley 106 and a rise and fall drive unit 110 is configured by these ball screw 102, the coupling member 103, the large pulley 104, the belt 105, the small pulley 106, and the motor-driven servo motor 107.

Incidentally, pad liners 1, 1, . . . which are slidably contacted with a base guide provided at a base (bed) of the press machine, not shown, are provided on each side face of the cushion pad 101.

A nut portion 102 a of the ball screw 102 is fixedly provided to a lower portion of the cushion pad 101, a threaded portion 102 b of the ball screw 102 is engaged with the nut portion 102 a, and the lower part of the threaded portion 102 b is connected to the coupling member 103. Further, the coupling member 103 is supported by a bearing, etc., to the beam 108 in the base, and the large pulley 104 is provided at the lower part of the coupling member 103. The small pulley 106 is provided at a rotary shaft of the motor-driven servo motor 107, and a belt 105 is wound on the large pulley 104 and the small pulley 106.

When the rotary shaft of the motor-driven servo motor 107 is rotated, the small pulley 106, the large pulley 104, the coupling member 103 and the threaded portion 102 b are operated to be rotated. When the threaded portion 102 b is rotated, the threaded portion 102 a is linearly moved in a vertical direction, that is, in a rising or falling direction along the threaded portion 102 b, and thereby the cushion pad 101 is raised or lowered together with the nut portion 102 a.

In the above-mentioned die cushion unit 100, the operation (rotation of the rotary shaft) of the motor-driven servo motor 107 constituting the rise and fall drive unit 110 is current controlled, and thereby the operation (pressure of a blank holder, stroke, locking position, etc.) of the cushion pad 101 can be suitably controlled, similarly to the oil pressure servo cylinder in the conventional die cushion unit.

FIG. 13 is a schematic view showing another embodiment of the die cushion unit. In a die cushion unit 200, a cushion pad 201 is interlocked to a motor-driven servo motor 207 through a ball screw 202, a coupling member 203, a large pulley 204, a belt 205 and a small pulley 206, and a rise and fall drive unit 210 is configured by these ball screw 202, the coupling member 203, the large pulley 204, the belt 205, the small pulley 206 and the motor-driven servo motor 207.

Incidentally, pad liners 1, 1, . . . slidably contacted with a base guide provided in a base (bed) of the press machine, not shown, are provided on each side face of the cushion pad 201.

A threaded portion 202 b of the ball screw 202 is fixed to a lower part of the cushion pad 201, a nut portion 202 a of the ball screw 202 is engaged with this threaded portion 202 b, and the coupling member 203 is connected to the lower part of the nut portion 202 a. Further, the coupling member 203 is supported by a bearing, etc., to the beam 208 in the base, a large pulley 204 is provided in the lower part of the coupling member 203, a small pulley 206 is provided on a rotary shaft of the motor-driven servo motor 207, and the belt 205 is wound on the large pulley 204 and the small pulley 206.

When the rotary shaft of the motor-driven servo motor 207 is rotated, the small pulley 206, the large pulley 204, the coupling member 203, and the nut portion 202 a are operated to be rotated. When the nut portion 202 a is operated to be rotated, the threaded portion 202 b is linearly moved in a vertical direction, that is, the rising and falling direction along the nut portion 202 a, and thereby the cushion pad 201 is operated to be raised or lowered together with the threaded portion 202 b.

Even in the above-mentioned die cushion unit 200, an operation of the motor-driven servo motor 207 constituting the rise and fall drive unit 210 is current-controlled to be rotated, an operation (pressure of a blank holder, locking position, etc.) of the cushion pad 201 can be controlled suitably, similarly to the oil pressure servo cylinder in a conventional die cushion apparatus.

FIG. 14 is a schematic view showing another embodiment of the die cushion unit. In this die cushion unit 300, a cushion pad 301 is coupled to a rotary shaft of a motor-driven servo motor 307 through a plunger rod 311 and a piston 312 and further through a ball screw 302, a coupling member 303, a large pulley 304, a belt 305, and a small pulley 306, and a rise and fall drive unit 310 is constructed by these plunger rod 311, the piston 312, the ball screw 302, the coupling member 303, the large pulley 304, the belt 305, the small pulley 306 and the motor-driven servo motor 307.

A columnar plunger rod 311 is fixed to the lower portion of the cushion pad 301, and this plunger rod 311 is slidably supported by a cylindrical plunger guide 313 fixed to a beam 308 in the base. The plunger rod 311 is operated to be raised or lowered while being supported, and the plunger guide 313 guides the plunger rod 311 and the cushion pad 301 coupled to the plunger rod 311 in the rising or falling direction.

A cylinder 311 a having an opening in a downward direction is formed at a lower part of the plunger rod 311, a piston 312 is slidably contained in the cylinder 311 a, an oil pressure chamber 314 is formed by the inner wall surface of the cylinder 311 a and the upper surface of the piston 312, and pressure oil is filed in this oil pressure chamber 314.

The oil pressure chamber 314 has its axial center which is the same as those of the plunger rod 311 and the ball screw 302, and further a pressure oil port of the oil pressure chamber 314 is connected to an oil pressure circuit, not shown, and the pressure oil communicates between the oil pressure chamber 314 and the oil pressure circuit. The pressure oil in the oil pressure chamber 314 alleviates an impact generated when the upper die is contacted with the work, and when an oil pressure becomes a predetermined value or more, the pressure oil is exhausted to a tank (not shown) to perform an overload protective function.

A lower end of the piston 312 is contacted with an upper end of the threaded portion 302 a in the ball screw 302. A spherical recess surface 312 a is formed on the lower end of the piston 312, and a spherical surface protrusion surface 302 c is formed on an upper end of the threaded portion 302 b opposed the recess surface 312 a. Incidentally, a protruding surface may be formed on the lower end of the piston 312, and a recess surface may be formed on the upper end of the threaded portion 302 b.

Here, a bar-like member like the threaded portion 302 b is strong against an axial force operating at an end part, but weak to a bending moment. When the upper end of the threaded portion 302 b is a spherical shape, even if the cushion pad 301 is inclined so that a bending moment is generated at the upper end of the threaded portion 302 b, only the axial force is operated at the threaded portion 302 b entirety, and a damage of the threaded portion 302 b due to the eccentric load can be prevented.

The nut portion 302 a is engaged with the threaded portion 302 b of the ball screw 302, and the lower portion of the nut portion 302 b is connected to the coupling member 303. Further, the coupling member 303 is supported to the beam 308 in the base by bearing, etc., and the large pulley 304 is provided at a lower portion of the coupling member 303. The small pulley 306 is provided at a rotary shaft of the motor-driven servo motor 307, and the belt 305 is wound on the large pulley 304 and the small pulley 306.

When the rotary shaft of the motor-driven servo motor 307 is rotated, the small pulley 306, the large pulley 304, the coupling member 303 and the nut portion 302 a are operated to be rotated. When the nut portion 302 a is rotated, the threaded portion 302 b is linearly moved in a vertical direction, that is, a raising or lowering direction along the nut portion 302 a, and the cushion pad 301 is operated to be raised or lowered together with the threaded portion 302 b, the piston 312, and the plunger rod 311.

In the above-mentioned die cushion unit 300, the operation of the motor-driven servo motor 307 constituting the rise or fall drive unit 310 is current-controlled, and the operation (pressure of a blank holder, stroke, locking position, etc.) of the cushion pad 301 can be suitably controlled, similarly to the oil pressure servo cylinder in the conventional die cushion apparatus.

FIG. 15 is a schematic view showing another embodiment of the die cushion unit. In this die cushion unit 400, a cushion pad 401 is coupled to a rotary shaft of a motor-driven servo motor 407 through a plunger rod 411 and a piston 412 and further through a ball screw 402, a coupling member 403, a coupling 421 and a reduction gear 422, and a rise and fall drive unit 410 is constructed by these plunger rod 411, the piston 412, the ball screw 402, the coupling member 403, the coupling 421, the reduction gear 422 and the motor-driven servo motor 407.

The motor-driven servo motor 407 is installed on a lower region of the coupling member 403, and the reduction gear 422 is connected to the rotary shaft of the motor-driven servo motor 407. Incidentally, the motor-driven servo motor 407 may include a reduction gear.

An output shaft of the reduction gear 422 is connected to the lower portion of the coupling member 403 through the coupling 421, and the ball screw 402, the coupling member 403, the coupling 421, and the output shaft of the reduction gear 422 are coaxially disposed. Further, according to a structure of the reduction gear 422, a rotary shaft of the motor-driven servo motor 407 is also disposed coaxially with the ball screw 402, etc.

Here, the die cushion unit 400 is fundamentally the same in the structure as the die cushion unit 300 described above except a layout of the motor-driven servo motor 407 to the coupling member 403, and a transmission mechanism of a power from the motor-driven servo motor 407 to the coupling member 403, and, therefore, in the constituting elements of the die cushion unit 400, having the same operation as the die cushion unit 300 are attached by numerals of 400 order adding 100 to the same numerals in FIG. 14, and a detailed description will be omitted.

In the die cushion unit 400, when the rotary shaft of the motor-driven servo motor 407 is rotated, a gear, etc. in the reduction gear 422 are rotated, the output shaft of the reduction gear 422, the coupling 421, the coupling member 403, and the nut portion 402 a are operated to be rotated. When the nut portion 402 a is rotated, the threaded portion 402 b is linearly moved in a vertical direction, that is, in a raising and lowering direction along the nut portion 302 a, and thereby the cushion pad 401 is operated to be raised or lowered together with the threaded portion 402 b, the piston 412, and the plunger rod 411.

Even in the above-mentioned die cushion unit 400, the operation of the motor-driven servo motor 407 constituting a rise and fall drive unit 410 (the rotation of the rotary shaft) is current-controlled, and the operation of the cushion pad 401 (pressure of a blank holder, stroke, locking position, etc.) of the cushion pad 401 can be suitably controlled, similarly to the oil pressure servo cylinder in the conventional die cushion apparatus.

Incidentally, in the above-mentioned embodiments, the example in which the present invention is applied to the press machine for building a production facility of an automobile has been described. However, the die cushion apparatus according to the present invention can be effectively applied not only to the production facility of the automobile, but also the press machine for building the production facility of various products. 

1. A die cushion apparatus of a press machine, comprising: a plurality of die cushion units each having a cushion pad and an elevating drive unit that vertically moves the cushion pad, wherein all the die cushion units are aligned in a line in a bed in a direction perpendicular to a work conveying direction in a positional state for use simultaneously in one step of pressing, and the cushion pad of at least one die cushion unit moves in a vertical direction individually and independently from other of the cushion pads of the plurality of die cushion units.
 2. The die cushion apparatus of the press machine according to claim 1, further comprising a control unit individually and independently controlling the plurality of die cushion units.
 3. The die cushion apparatus of the press machine according to claim 2, wherein the control unit controls the plurality of die cushion units in synchronism with each other that are operated for a work common to each other.
 4. The die cushion apparatus of the press machine according to claim 1, wherein the plurality of die cushion units operate synchronously with each other for forming different works.
 5. The die cushion apparatus of the press machine according to claim 2, wherein the control unit controls the plurality of die cushion units to operate synchronously with each other for forming different works.
 6. The die cushion apparatus of the press machine according to claim 2, wherein, when a width of a work in the alignment direction of the plurality of die cushion pads is narrow, the control unit controls only the cushion pad that is located at a press center. 